Flame-retardant and electromagnetic interference attenuating thermoplastic resin composition

ABSTRACT

A flame-retardant and electromagnetic wave-shielding thermoplastic resin composition is provided, which comprises 100 parts by weight of a thermoplastic resin (A); from 0.5 to 30 parts by weight of a flame retardant of a halogen-free phosphate (B) represented by the following general formula (1): 
                         
wherein R 1 , R 2 , R 3 , and R 4  each independently represent a hydrogen atom or a monovalent organic group, at least one of R 1 , R 2 , R 3 , and R 4  is a monovalent organic group, X is a bivalent organic group, k, l, m, and n are each independently 0 or 1, and N is an integer of 0 to 10; from 5 to 35 parts by weight of a metal-coated fiber (C); and from 3 to 30 parts by weight of a filler in a scaly shape or an acicular shape (D). Such a composition has excellent flame retardance, good appearance, and excellent molding flowability.

TECHNICAL FIELD

The present invention relates to a flame-retardant and electromagneticwave-shielding thermoplastic resin composition that is excellent inflame retardance and molding flowability.

BACKGROUND ART

Styrene resins, which are manufactured and commercially available underthe name of HIPS, ABS etc., are excellent in appearance, mechanicalproperties and molding flowability, and therefore used in various fieldssuch as vehicle components, electrical appliances, miscellaneous goods,etc.

Since these styrene resins are thermoplastic materials, however, the useof them is restricted in electrical and electronic equipment that isrequired to have flame retardance such as the self-extinguishingproperties (V-0, V-1, and V-2 classes) according to U.S. UnderwritersLaboratories (UL) Standard 94.

The flame retardance is provided by using halide compounds such astetrabromobisphenol A (TBBA) and decabromodiphenylether (DBDE), acombination of halides and antimony compounds, or various phosphorouscompounds.

Although the addition of these compounds can provide the flameretardance, an increase in the used amount of such expensive fireretardants leads to not only an increase in cost but also a significantdeterioration in the physical properties such as impact resistance,which is one of the distinctive properties of the styrene resins. Inaddition, antimony trioxide, which is used in combination of the halidecompounds, is a material of concern about environmental pollution.Therefore, some cases require the flame-retardant resin materials to befree of the antimony compound.

In some uses of the flame-retardant resin materials, such as householdelectrical appliances, OA, and electrical and electronic equipment, somecomponents are required to have an electromagnetic wave-shieldingproperty (EMI shielding property). In most of such uses, the resinmaterials are subjected to a secondary process such as plating,conductive coating, or the like, before used. Some electromagneticwave-shielding thermoplastic resins are commercially available,including thermoplastic resins that contain the additive for increasingelectrical conductivity, such as carbon fiber, carbon black, andstainless steel fiber. However, no thermoplastic resin is available tosatisfy all of flame retardance, electromagnetic wave-shieldingstability, and good molding appearance.

The present invention has been made to solve the above problems. It istherefore an object of the present invention to provide aflame-retardant and electromagnetic wave-shielding, thermoplastic resincomposition that has excellent flame retardance, good appearance, andexcellent molding flowability.

The inventors have made active investigations in light of the aboveproblems and have found that the use of a specific flame retardant, ametal-coated fiber, and a specifically shaped filler in a specificamount range of composition can provide a flame-retardant andelectromagnetic wave-shielding, thermoplastic resin composition withexcellent flame retardance, good appearance, and excellent moldingflowability, and have finally made the present invention.

DISCLOSURE OF THE INVENTION

Thus, the present invention is directed to a flame-retardant andelectromagnetic wave-shielding thermoplastic resin compositioncomprising:

(A) 100 parts by weight of a thermoplastic resin;

(B) 0.5 to 30 parts by weight of a flame retardant of a halogen-freephosphate ester represented by the following general formula (1):

wherein R₁, R₂, R₃, and R₄ each independently represent a hydrogen atomor a monovalent organic group, at least one of R₁, R₂, R₃, and R₄ is amonovalent organic group, X is a bivalent organic group, k, l, m, and nare each independently 0 or 1, and N is an integer of from 0 to 10;

(C) 5 to 35 parts by weight of a metal-coated fiber; and

(D) 3 to 30 parts by weight of a filler in a scaly shape or an acicularshape.

The flame-retardant and electromagnetic wave-shielding thermoplasticresin composition of the present invention is described in detail in thefollowing.

Examples of the thermoplastic resin used in the present inventioninclude styrene resin such as polystyrene, AS resin, MS resin, HIPSresin, ABS resin, AES resin, AAS resin, and MBS resin; polycarbonateresin; polybutyleneterephthalate resin; polyethyleneterephthalate resin;polyamide resin; polyethylene resin; polypropylene resin;polyphenylenether resin; polyphenylenesulfide resin; andpolyoxymethylene resin. Among these resins, the styrene resins or amixture of the styrene resin and any of the other thermoplastic resinsis particularly preferred. The content of the styrene resin in thethermoplastic resin (A) is preferably 10 to 100% by weight. Inparticular, a preferred styrene resin is a rubber-reinforced styrenetype resin such as ABS resin, AES resin, AAS resin, and MBS resin.

In the general formula (1) representing the halogen-free phosphate ofthe flame retardant (B) used for the present invention, the monovalentorganic group may include an optionally substituted alkyl group, anoptionally substituted aryl group, and an optionally substitutedcycloalkyl group. Examples of the substituent in the substituted groupinclude an alkyl group, an alkoxy group, an alkylthio group, an arylgroup, an aryloxy group, and an arylthio group, and the substituent mayalso be any combination of these groups (such as an arylalkoxyalkylgroup) or any combination of these groups in which the groups arecombined through an atom such as oxygen, sulfur, or nitrogen (such as anarylsulfonylaryl group). Examples of the bivalent organic group includean alkylene group, an optionally substituted phenylene group, and thegroups derived from polyhydric phenols or polynuclear phenols (such asbisphenols). Particularly preferred examples of the bivalent organicgroup include hydroquinone, resorcinol, diphenylol methane, diphenyloldimethylmethane, dihydroxydiphenyl, p,p′-dihydroxydiphenylsulfone, anddihydroxynaphthalene. One or more thereof may be used.

Examples of the flame retardant of the halogen-free phosphate (B)include trimethyl phosphate, triethyl phosphate, tripropyl phosphate,tributyl phosphate, tripentyl phosphate, trihexyl phosphate,tricyclohexyl phosphate, trioctyl phosphate, triphenyl phosphate,tricresyl phosphate, trixylenyl phosphate, hydroxyphenyldiphenylphosphate, cresyldiphenyl phosphate, xylenyldiphenyl phosphate, and thecompound represented by the following formula (2), (3), or (4).

wherein R represents hydrogen or a methyl group.

The amount ratio of the flame retardant of the halogen-free phosphate(B) is from 0.5 to 30 parts by weight based on 100 parts by weight ofthe thermoplastic resin (A). When a ratio is less than 0.5 parts byweight, no sufficient flame retardance can be obtained. A ratio is morethan 30 parts by weight is not preferred, because such a ratio leads toa decrease in heat resistance and impact resistance.

In the present invention, the flame retardant of the phosphaterepresented by the formula (1) is used to achieve the desired effect. Asfar as the effect of the present invention is not deteriorated, however,a halogen-free flame retardant other than the phosphate, such asmelamine cyanurate, a phosphazene derivative, and ammoniumpolyphosphate; a halogenated flame retardant such as TBBA and ahalogenated triazine compound, or a flameproofing agent such as anantimony compound may be added, though the added amount of thehalogenated flame retardant and the antimony compound should be as smallas possible.

Examples of the metal-coated fiber (C) include nickel-coated carbonfiber and nickel-coated glass fiber. The nickel-coated carbon fiber isparticularly preferred. In the present invention, as far as the effectis not deteriorated, conventional carbon fiber, glass fiber, or the likemaybe added together with the metal-coated fiber. The amount ratio ofthe metal-coated fiber (C) is from 5 to 35 parts by weight based on 100parts by weight of the thermoplastic resin (A). When a ratio is lessthan 5 parts by weight, the electrical conductivity is not enough todevelop the electromagnetic wave-shielding property. A ratio more than35 parts by weight is not preferred, because such a ratio leads to areduction in molding flowability and impact resistance, and adeterioration in molding appearance.

Examples of the filler (D) in the scaly shape or the acicular shape usedin the present invention include talc, mica, glass flake, graphite (inthe scaly shape), and a whisker (in the acicular shape) of potassiumtitanate, magnesium oxysulfate, aluminum borate, wollastonite, acicularcalcium carbonate, zinc oxide, silicon carbide, or silicon nitride. Ofthese materials, zincoxide whisker is particularly preferred. The amountratio of the component (D) is from 3 to 30 parts by weight based on 100parts by weight of the thermoplastic resin (A). A ratio less than 3parts by weight leads to a deterioration in molding appearance and areduction in electromagnetic wave-shielding stability. A ratio more than30 parts by weight is not preferred, because such a ratio leads to areduction in molding flowability and impact resistance.

In the present invention, polytetrafluoroethylene (E) is also preferablyused in addition to the above (A), (B), (C), and (D) components toenhance the flame-retardant effect. The polytetrafluoroethylene (E) is afluoro-polymer formed by the polymerization of the main component oftetrafluoroethylene, for example, including commercially availablePOLYFLON (trade name) manufactured by DAIKIN INDUSTRIES, LTD., Teflon®manufactured by Du Pont-Mitsui Fluorochemicals Co., LTD., and Hostaflon®manufactured by Hoechst AG. The polytetrafluoroethylene (E) ispreferably used in the range of 0.05 to 5 parts by weight based on 100parts by weight of the thermoplastic resin (A).

In the present invention, any process may be used without limit formixing the components, and an extruder, a Banbury mixer, a roller, akneader, or the like can be used for mixing.

The resin composition of the present invention may optionally contain aknown additive such as an antioxidant such as2,6-di-t-butyl-4-methylphenol,2-(1-methylcyclohexyl)-4,6-dimethylphenol,2,2-methylenebis-(4-ethyl-6-t-methylphenol),4,4′-thiobis-(6-t-butyl-3-methylphenol), dilaurylthiodipropionate, andtris (di-nonylphenyl)phosphite; an ultraviolet absorbing agent such asp-t-butylphenyl salicylate, 2,2′-dihydroxy-4-methoxybenzophenone, and2-(2′-hydroxy-4′-n-octoxyphenyl)benzotriazole; a lubricant such asparaffin wax, stearic acid, hardened oil, stearoamide,methylenebis(stearoamide), ethylenebis(stearoamide), n-butylstearate,ketonewax, octylalcohol, laurylalcohol, and hydroxystearic acidtriglyceride; a coloring agent such as titanium oxide and carbon black;and a filler such as calcium carbonate, clay, silica, glass fiber, glassbead, and carbon fiber.

The above-described resin composition of the present invention may beformed into a molding product with an excellent flame retardance and anexcellent electromagnetic wave-shielding property by a known moldingmethod such as injection molding, compression molding, extrusionmolding, and injection compression molding. The resultant moldingproduct can be used in the field demanding flame retardance andelectromagnetic wave-shielding property, for example, as a component ora housing component of an electrical or electronic device.

EXAMPLES

The present invention is further described in detail by showing Examplesin the following, but such Examples are not intended to restrict thescope of the present invention. In Examples, “parts” or “%” is byweight, unless otherwise specified.

In the following, Examples and Comparative Examples are shown for thepurpose of illustrating the present invention, but such Examples are notintended to restrict the scope of the present invention. The followingmethods were carried out for the evaluation of the products related tothe present invention.

Molding Flowability:

The melt flow rate was measured according to ASTM D-1238 at 220° C.×10kg, units: g/10 min.

Impact Resistance:

The impact strength was measured without notch according to ASTM D-256with ¼ inch, units: J/m.

Flame Retardance:

The flame retardance (self-extinguishing property) was measured witheach test piece 1.6 mm in thickness according to UL 94.

Electromagnetic Wave (EMI) Shielding Property:

Flat-shaped test pieces, each 150 mm long, 100 mm wide, and 3 mm thick,were prepared by injection molding, and a center portion, 50 mm×50 mm,was cut out of each of the prepared pieces to form a test piece formeasurement. The volume resistance (electrical conductivity) wasmeasured in units of Ω·cm to evaluate the electromagnetic wave-shieldingproperty.

Molding Appearance:

Flat-shaped test pieces, each 150 mm long, 100 mm wide, and 3 mm thick,were prepared by injection molding, and the appearance thereof wasvisually observed.

-   ◯: There is neither flow mark in the resin nor floating of the metal    fiber.-   Δ: There is either flow mark in the resin or floating of the metal    fiber.-   X: There are both flow mark in the resin and floating of the metal    fiber.

Thermoplastic Resin (A)

A-1: ABS Resin (KRALASTIC® GA-501 manufactured by NIPPON A&L INC.)

A-2: Mixture of the above ABS Resin and Polycarbonate Resin (CALIBRE200-20 manufactured by Sumitomo Dow Limited.) at a ratio of 80 to 20 byweight.

A-3: PA/ABS Resin Alloy (TECHNIACE® TA-1500 manufactured by NIPPON A&LINC.)

Phosphate Flame Retardant (B)

B-1: Compound Represented by Formula (2) (CR-733S manufactured byDAIHACHI CHEMICAL INDUSTRY CO., LTD.)

B-2: Compound Represented by Formula (4) (PX-200 manufactured byDAIHACHI CHEMICAL INDUSTRY CO., LTD.)

B-i: Tetrabromobisphenol A

B-ii: Antimony Trioxide

B-iii: Phenoxyphosphazene (CP-134H manufactured by Chemipro KaseiKaisha, Ltd.)

Metal-Coated Fiber (C)

C-1: Nickel-Coated Carbon Fiber (Besfight MCHTA-C6-US manufactured byToho Rayon Ltd.)

C-i: Carbon Fiber (Besfight HTA-C6-SR manufactured by Toho Rayon Ltd.)

Filler (D)

D-1: Zinc Oxide Whisker (Pana-Tetra manufactured by Matsushita AMTECCo., Ltd.)

Polytetrafluoroethylene (E)

E-1: PTFE (POLYFLON FA-500 manufactured by DAIKIN INDUSTRIES, LTD.)

Examples 1 to 45 and Comparative Examples 1 to 7

The above components (A) to (E) were mixed in each ratio as shown inTable 1, and the mixture was melted and kneaded with a biaxial extruder,resulting in a pellet. The resulting pellet was formed into each testpiece with an injection molder, and then each evaluation was carriedout. The results are shown in Table 1.

TABLE 1 Ex- Ex- Ex- Ex- Ex- Compara- Compara- Compara- Compara- Compara-Compara- Compara- ample ample ample ample ample tive tive tive tive tivetive tive 1 2 3 4 5 Example 1 Example 2 Example 3 Example 4 Example 5Example 6 Example 7 Composition A-1 100 100 100 100 100 100 A-2 100 100100 100 100 A-3 100 B-1 3 12 3 3 0.1 3 B-2 12 15 12 50 12 B-i 15 15 20B-ii 5 5 B-iii 20 C-1 10 20 15 15 15 10 1 15 15 10 50 C-i 20 D-1 5 10 1010 5 5 10 1 10 5 10 10 E-1 0.3 0.3 0.3 0.3 Physical Properties Molding40 25 40 24 30 10 50 33 8 100 3 17 flowability (g/10 min) Impact 147 245143 255 150 196 275 294 98 35 39 210 Resistance (J/m) Flame V-0 V-0 V-2V-0 V-0 HB V-0 V-0 HB HB HB V-0 Retardance Electromag- 15 1 10 3 12 101000< 150 5 120 1 140 netic Wave-Shield- ing Property (Ω · cm) Molding ∘∘ ∘ ∘ ∘ ∘ ∘ x Δ ∘ x Δ Appearance

As described above, the flame-retardant and electromagneticwave-shielding thermoplastic resin composition of the present inventioncan have excellent flame retardance, good appearance, and excellentmolding flowability, and therefore can appropriately be used in thefield demanding flame retardance and electromagnetic wave-shieldingproperty, such as household electrical appliances, OA devices, andelectrical or electronic devices.

1. A flame-retardant and electromagnetic wave-shielding thermoplasticresin composition, comprising: 100 parts by weight of a thermoplasticresin (A); from 0.5 to 30 parts by weight of a flame retardant of ahalogen-free phosphate (B) represented by the following general formula(1):

wherein R₁, R₂, R₃, and R₁ each independently represent a hydrogen atomor a monovalent organic group, at least one of R₁, R₂, R₃, and R₄ is amonovalent organic group, X is a bivalent organic group, k, l, m, and nare each independently 0 or 1, and N is an integer of 0 to 10; from 5 to35 parts by weight of a metal-coated fiber (C); from 3 to 30 parts byweight of a filler in a scaly shape or an acicular shape (D), and from0.05 to 5 parts by weight of polytetrafluoroethylene (E), wherein thethermoplastic resin (A) comprises a styrene resin or a styrene resin anda second thermoplastic resin, wherein the styrene resin is an ABS resin,an AES resin, an AAS resin or an MBS resin; the second thermoplasticresin is a polycarbonate resin or a polyamide resin; and the component(D) is a zinc oxide whisker.
 2. A molding product formed of the resincomposition according to claim
 1. 3. The molding product according toclaim 2, wherein the product has a volume resistance value of at most100 Ω·cm.
 4. A component or housing component product of an electricalor electronic device, comprising the molding product according to claim2.